This invention relates to pigment dispersants, which are easy to prepare and are useful for dispersing a wide variety of pigments.
Pigments are frequently dispersed as fine particles into a liquid medium for use in inks and coatings, as well as plastics, cosmetics, adhesives, and the like. For that purpose, it is desirable for the pigment to be dispersed as finely and as rapidly as possible into the liquid medium and remain as a stable fine dispersion over time for optimum results. Unfortunately, the dispersion of fine particles in liquids is unstable, i.e., the particles tend to agglomerate or flocculate causing uneven pigmentation in the product being colored.
Numerous pigment dispersants have been developed in order to minimize the effects of agglomeration and/or flocculation. They have been used to form pigment dispersions that are used in a variety of water borne and solvent borne coating compositions. Examples of U.S. Patents describing dispersants and pigment dispersants include U.S. Pat. Nos. 4,496,686, 4,673,705, 4,754,056, 5,034,444, 5,424,364, 6,037,414, 6,451,950, 6,495,618, and 6,878,799.
The dispersants act to lower the viscosity of pigment dispersions, which makes it possible for more pigment to be employed, thereby affording very concentrated dispersions which can be satisfactorily handled and dispersed. However, although the pigment concentration increases linearly, the viscosity of the dispersion increases exponentially and the upper limit of pigment concentration in the dispersion is determined by the viscosity. When the viscosity becomes too high, a pigment can no longer be dispersed satisfactorily or easily handled during ink or coating manufacturing. In addition, the system experiences a heat buildup due to the frictional forces that occur during the dispersion process. This can be detrimental to quality because the increase in temperature can cause degradation of certain pigments. Incorporation of the appropriate dispersant also helps to neutralize such defects by providing a more efficient wetting and deflocculating of the pigment, and affording a more stable dispersion.
The present invention provides new pigment dispersants.